The Claim
Nine weeks of high-load or low-load resistance training, with consistent training volume and effort to failure, does not result in a significant increase in pectoralis major muscle thickness in recreationally trained males.
What the research says
Supports is higher
Support is ahead, but a single strong opposing study can change this.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
After nine weeks of weight training with either heavy or light weights, muscle thickness in the chest does not change significantly in men who train regularly but are not elite athletes.
See the scientific wording
Muscle thickness in the pectoralis major does not significantly increase after nine weeks of either high-load or low-load resistance training in recreationally trained males, despite consistent training volume and effort to failure.
In men who already train regularly, their chest muscles have already grown as much as they can with normal training, so even doing heavy or light weights to exhaustion doesn't make them bigger. The muscles respond to effort and tension the same way no matter the weight, but their ability to grow further is blocked because they've already reached their natural limit for growth under these conditions.
What the research says
1 studyIn men who train regularly but aren't bodybuilders, doing weight training with either heavy or light weights for nine weeks didn't make their chest muscles get thicker — both groups stayed about the same.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.